I'm having problems using Nietzsche correctly. She seems to be my weakest character and I'm not sure why. I put her in against unit types she's strong against, use good cards and she's still getting her tail kicked way more often then my other characters.

Wow... Your Neitzsche is really weak. Do you ever feed her? Her stats is really low.

What "good cards" are you using? The best card Nietzsche could use is Blizzard. If she is equipped with Icicle Spear, its Fatal Damage. If she is against Griffons, AND is equipped with Icicle Spear, its Overkill.

Seems like to me that you have messed up with her stats. You can equip characters with food items, that boosts stats up with 1 Big Star.